Peugeot planet can test the fans via the ecu outputs
but do check the fuses first as i think there are three fo the hdi system
and yes it is likely that 1 fan has packed up not letting the fans work at slow speed
easy to test though via the relay sockets with the relays removed
i had an issue with one fan fubard so one only worked at full speed and none at low speed
replaced the faulty fan and now both work
drawings here for the hdi 3 plug ECU
http://306oc.co.uk/forum/thread-11246-po...#pid223155
but do check the fuses first as i think there are three fo the hdi system
and yes it is likely that 1 fan has packed up not letting the fans work at slow speed
easy to test though via the relay sockets with the relays removed
i had an issue with one fan fubard so one only worked at full speed and none at low speed
replaced the faulty fan and now both work
drawings here for the hdi 3 plug ECU
http://306oc.co.uk/forum/thread-11246-po...#pid223155